
where \(\sigma _{zz}^{(0)}\)  is the conductivity in absence of any magnetic field, while \(\sigma _{zz}^{(2)}\)  is the quadratic coefficient of magnetic field dependence. In contrast to earlier anticipation that the quadratic coefficient \(\sigma _{zz}^{(2)}\)  is always positive, it was recently realized that the coefficient can become negative if the intervalley scattering is sufficiently strong [1]}. In other words, large intervalley scattering results in negative longitudinal magnetoconductivity or reverses its sign. Specifically this occurs above a critical intervalley scattering strength \(\alpha _c\) . The sign of the parameter \(\sigma _{zz}^{(2)}\)  also correlates with increasing or decreasing longitudinal magnetoconductivity. We can call this as the usual `sign-reversal' of LMC, which refers to the fact that \(\sigma _{zz}(|B|)-\sigma _{zz}(B=0)\)  continuously changes sign from positive to negative.
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